。
She'll probably make him a fine wife.
Literal
She [topic-は] his [genitive-の] good wife [into-に] become [probably-だろう].
Notable for using 奥さん ('wife') rather than the more neutral 妻. 奥さん is the polite/respectful word for someone else's wife — picking it here makes the sentence's perspective subtly outside the relationship, addressing the listener about her future role. 奥 literally means 'interior, inner part,' and the term reflects the historical role of wives keeping the inner household. The Xになるだろう pattern projects the future state — 'will probably become.'